Process and device for flash smelting sulphide ores or concentrates

ABSTRACT

A process and device to be used in the flash smelting of sulphide ores or concentrates is disclosed, wherein molten matte is fed, possibly after granulation, into an oxidation zone together with air and/or oxygen, whereafter the hot roasting gases are fed into the upper part of the reaction zone of a flash smelting furnace together with fuel and ore or concentrate. The reaction space or bed in the oxidation furnace is cooled or the air and/or oxygen is pre-heated before it is fed into the oxidation zone in order to control the oxidation capacity of the oxidation furnace and the smelting capacity of the flash smelting furnace and to relate the capacities to each other.

United States Patent 1 Nermes et al.

1 1 PROCESS AND DEVICE FOR FLASH SMELTING SULPHIDE ORES OR CONCENTRATES[75] Inventors: Esko Olavi Nermes; Timo Tapani Talonen, both of Kokkola;Olavi August Aaltonen, Pori, all of Finland [73] Assignee: OutokumpuOy,Outokurnpu,

Finland [22] Filed: Oct. 24, 1973 [2]] Appl. No.: 409,261

[30] Foreign Application Priority Data Oct. 26, 1972 Finland 2977/72[52] US. Cl. 75/23; 75/74; 75/92; 266/25 {51] Int. Cl. C2lb 1/04; C22b1/10 [58] Field of Search 75/9, 23, 7375, 75/92; 266/25 [56] ReferencesCited UNITED STATES PATENTS 852,612 5/1907 Perkins 75/23 X 1,845,5032/1932 Legrand 75/92 1,860,585 5/1932 Lenander 75/23 X 2,219,411 10/1940Carlsson 75/23 X 2,438,91 l 4/1948 Gronningsaeter 75/74 X 1 July 1, 19752,699,375 1/1955 .lohannsen et a1. 75/23 X 2,819,157 1/1958 Fischer v75/9 3,193,602 8/1965 Wittmann. 75/9 X 3,463,630 8/1969 Todd 75/233,754,891 8/1973 Bryk et al. 75/74 X 3,773,494 11/1973 Tuwiner r..'75/23 3,790,366 2/1974 Bryk et a1. 75/74 X 3,792,998 2/1974 Norro75/74 X Primary ExaminerA. B. Curtis Assistant ExaminerThomas A. WaltzAttorney, Agent, or Firm-Brooks Haidt Haffner & DeLal-lunt [57] ABSTRACTA process and device to be used in the flash smelting of sulphide oresor concentrates is disclosed, wherein molten matte is fed, possiblyafter granulation, into an oxidation zone together with air and/oroxygen, whereafter the hot roasting gases are fed into the upper part ofthe reaction zone of a flash smelting furnace together with fuel and oreor concentrate. The reaction space or bed in the oxidation furnace iscooled or the air and/or oxygen is pre-heated before it is fed into theoxidation zone in order to control the oxidation capacity of theoxidation furnace and the smelting capacity of the flash smeltingfurnace and to relate the capacities to each other.

12 Claims, 5 Drawing Figures SHEET W 90% F bGQQ SHEET ar a 07900rcducf/an process Mien using ai a! m 6 3a.:- a/ furnar A: m0 000 A/m%Fig. 2

PROCESS AND DEVICE FOR FLASH SMELTING SULPHIDE ORES OR CONCENTRATESBACKGROUND OF THE INVENTION 1. Field of the Invention The inventionrelates to a process and device to be used in the flash smelting ofsulphide ores or concentrates.

2. Description of the Prior Art In the currently usedoxidation-reduction process, pyrite is suspended in hot, oxygenous smokegases at the upper end of the reaction shaft of a flash smeltingfurnace. Both a thermal decomposition of the pyrite and a simultaneouspartial oxidation of the sublimated sulphur and the iron matte producedin the sublimation process take place in the suspension. The hot,oxygenous smoke gases are obtained by burning oil with a high aircoefficient.

The products of the reactions in the reaction shaft are a gas whichcontains the following compounds, among others: 5 S H 8, COS, H and Co,and a melt which consists of FeS, iron oxides and slag. The sulphurcontent of the gas is produced in the form of elemental sulphur, themelt is granulated and roasted into gaseous sulphur dioxide and ironore.

The sulphur content in the melt (the rate of iron oxides) is dependenton the oxygen content in the smoke gases fed into the reaction shaft,which again can be regulated by regulating the air coefficient of theoil burning process. By increasing the air coefficient (by decreasingthe rate of oil) a larger part of the sulphur present in the concentratecan be released from the concentrate and directed into the gas.

Owing to the more oxidating reaction shaft operation, the rate ofsulphur dioxide increases and those of the reducing components (H 8,COS, H CO) decrease. The optimal recovery of sulphur prerequires thatthe gas composition realizes the following equation:

50 V2 (H 5 +COS H +CO) For this reason the excess S0 has been reducedwith light petroleum in the rising shaft of the flash smelting furnace.

The sulphur content in the produced iron matte can be lowered by raisingthe oxygen content in the gas to be fed into the reaction shaft. Theratio between the production of elemental sulphur and that of gaseoussulphur dioxide can thus be regulated by the reaction shaft oil feed theair rate being constant. The rate of oil used in the reaction shaftburners does not have a significant effect on the smelting capacity ofthe system (FIG. 2).

The air coefficient of the oil burning also affects the fuel consumptionin the process. When the operation takes place at the optimal point inregard to the sulphur yield, all the oxygen fed into the reaction shaftin the combustion air must become bound either to the iron removed alongwith the iron matte or to the carbon and hydrogen of the fuel and thereduction agent. When the air coefficient rises and the sulphur contentof the iron matte lowers, the oxygen content of the matte increases andthe sum of the requisite oil and reduction petroleum decreases.

In this known oxidation-reduction process it is not possible toefficiently use in the process the heat of combustion of theconcentrate. The heat generated in the roasting of the iron matte isproduced in the form of high-pressure steam. The rate of air used in theprocess is high because air is used both at the smelting and theroasting stages.

It is also known that the roasting capacity of a roasting furnace per secan be increased by cooling the fluidized bed by means of coolingdevices. The cooling of the bed results in a reduction of excess air inthe roasting furnace and a reduction of the content of free oxygen inthe roasting gas. The roasting capacity of a roasting furnace at aconstant air rate can be reduced further, and the oxygen content in theroasting gas can be increased by pre-heating the roasting air.

SUMMARY OF THE INVENTION According to the invention a decisiveimprovement is achieved when a so-called sulphur circulation process isadopted in which the iron matte obtained from the flash smelting furnaceis roasted either in its entirety or partially in a roasting furnace,from which all the roasting gases are fed, uncooled, into the flashsmelting furnace for the smelting of fresh concentrate.

The following advantages are gained in the process:

The consumption of the reduction agent and/or fuel decreases. This isbecause the rate of oxygen coming into the flash smelting furnace islower since part of the oxygen becomes bound to iron in the roastingfurnace.

DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic side view of adevice fitted in connection with a flash smelting furnace according tothe invention,

FIG. 2 shows, among other things, the feeds of fuel, reduction agent andconcentrate as functions of the oil fed into the reaction shaft.

FIGS. 3 and 4 shows the roasting air as a function of pre-heating, and

FIG. 5 the fluidized bed of the roasting furnace as a function ofcooling.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The smelting capacity of theflash smelting furnace is mainly dependent on the content of free oxygenin the gas used and on the temperature of the gas. A rise in thetemperature and the oxygen content increases the smelting capacity ofthe flash smelting furnace.

When in the present process the gas obtained from the roasting furnaceis used in the flash smelting furnace for smelting pyrite, the low rateof free oxygen in the gas has a decreasing effect on the flash smeltingfurnace capacity. A high gas temperature again increases the smeltingcapacity in comparison to cold air. With the joint effect of these twoand by using an uncooled roasting furnace, a smelting capacity which isapproximately the same as when using cold air is obtained in the flashsmelting furnace.

It is obvious from the above that in this process the capacities of thesmelting furnace and the roasting furnace can be controlled by means ofcooling devices placed in the fluidized bed in the roasting furnace orby pre-heating the roasting air. Cooling the bed increases the roastingcapacity of the roasting furnace and decreases the smelting capacity ofthe flash smelting furnace. Pre-heating the roasting air produces theopposite effect.

By choosing an appropriate degree of cooling the roasting furnace, thecapacities of the roasting furnace and the flash smelting furnace can bebalanced so that the rate of melt produced by the flash smelting furnacecorresponds to the capacity of the roasting furnace. In this case allthe sulphur present in the concentrate is obtained in the form ofelemental sulphur. By lowering the degree of cooling of the roastingfurnace or by further pre-heating the roasting air, the desiredproportion ofthe iron matte produced in the flash smelting furnace isleft for roasting in another roasting furnace to produce gaseous sulphurdioxide (FlGS. 3 and 4).

The capacity of the flash smelting furnace can be raised withoutsignificantly affecting the capacity of the roasting furnace, byenriching the roasting air or the roasting gas with oxygen. In this casea higher degree of cooling is required for the roasting furnace in orderthat the roasting furnace capacity correspond to the iron matte outputof the flash smelting furnace. The correspondence is achieved with agreater smelting capacity (FIG. 5).

When copper or nickel concentrate is used as feed in theoxidation-reduction process, the excess oxygen in the reaction shaftmust be sufficient, because the slagging of iron at the smelting stagerequires a high oxygen pressure in comparison to the pyrite process.When copper concentrate is used in the process according to theinvention. the treatment of the copper matte from the flash smeltingfurnace takes place in a previously known manner in a copper converter,the gases of which are then fed as such or concentrated in regard to Spossibly mixed with air, into the smelting stage of the flash smeltingfurnace. With this procedure, the entire sulphur content of the copperconcentrate is recovered as elemental sulphur.

In a preferred embodiment of the invention the lower limit of thetemperature of the oxidation zone is about 900C, which is defined by theignition point of the matte produced in the flash smelting furnace, andthe upper limit of 2,000C, which is defined by the heat resistance ofthe oxidation furnace.

The flash smelting furnace shown in FIG. 1 mainly comprises three parts.i.e., a vertical reaction shaft 1 and a rising shaft 3, the lower endsof which have been connected to the two ends of a horizontal lowerfurnace 2. The fuel and concentrate are fed through pipes 4 and 5 intothe upper part of the reaction shaft 1 and the reduction agent is fedthrough pipe 14 into the upper and lower parts of the rising shaft 3.Molten iron matte is removed from the lower furnace 2 through pipe 7into a granulating device 8. Part of the granulated iron matte is fedalong feed line 9 into the S0 production, and part of it along feed line10 into a suspension bed furnace 12 which works as a roasting furnaceand in which the temperature is about 1,000C. The reaction temperatureof the fluidized-bed furnace can be lowered by cooling devices 15, orthe air can be pre-heated. Air is also fed into the fluidized-bedfurnace through feed line 11, and the hot roasting gases are directedfrom the upper part of the fluidized-bed furnace through a cyclone I3and a connecting pipe 6 into the upper part of the reaction shaft l ofthe flash smelting furnace.

The gases at about 1,200C which emerge from the upper part of the risingshaft 3 are finally fed into the gas cooling. purification and catalysisstage where the elemental sulphur is recovered.

The oxygen content in the roasting gas to be fed into the upper part ofthe reaction shaft 1 is preferably about 5-18 percent and its sulphurdioxide content about 1-10 percent.

The lower limit of the oxygen content and the upper limit of the S0content are defined by the relation between the flash smelting andoxidation furnaces, Outside these limits the matte production of theflash smelting furnace is lower than the oxidation capacity of theoxidation zone.

The upper limit of the oxygen content and the lower limit of the S0content correspond to the lowest possible capacity of the oxidation zoneachieved by preheating the oxidant gas to be fed to the oxidation zone.

The process and device according to the invention can also be used forthe treatment of ores and concentrates other than pyrite, suchchalcopyrite.

What is claimed is:

l. [n a process for flash smelting a raw material se lected fromsulphide ores and concentrates. the steps of:

a. feeding into an oxidation zone molten matte from the flash smeltingfurnace and at least one oxidizing gas selected from the groupconsisting essentially of air and oxygen;

b. withdrawing roasting gases at roasting temperature from the oxidationzone;

c. feeding to an upper part of a reaction shaft of a flash smeltingfurnace said roasting gases together with fuel and said raw material;and

d. controlling temperature in the oxidation zone for maintaining theoxygen content in the roasting gases between about 5 percent and about18 percent by volume and for maintaining the S0 content in the roastinggases between about 1 percent and about 10 percent by volume to controlthe relationship between the oxidation capacity of the oxidation zoneand the smelting capacity of the flash smelting furnace reaction shaft.

2. The process of claim 1, comprising fluidizing the molten matte in theoxidation zone to a fluidized bed and controlling the temperature of theoxidation zone by cooling said bed.

3. The process of claim 1, comprising controlling the temperature of theoxidation zone by preheating the gas fed to the same.

4. The process of claim I, comprising controlling the temperature of theoxidation zone to a temperature of from 900C to 2,000C.

5. The process of claim I, further comprising separating solidsentrained in the roasting gases prior to feeding the roasting gases intothe flash smelting reaction zone.

6. In a flash smelting furnace of the type having a lower furnace, avertical reaction shaft at one end of the lower furnace, means forfeeding fuel and a raw material of sulphide ores or concentrates to theupper part of the vertical reaction shaft, and means for withdrawingmolten matte from the lower furnace:

a. an oxidation furnace;

b. means for feeding the molten matte from the lower furnace to theoxidation furnace;

c. means for feeding at least one gas selected from the group consistingessentially of air and oxygen to the oxidation furnace;

d. means for controlling the temperature of the oxidation furnace;

0. means for feeding hot roasting gases from the oxidation furnace tothe upper part of the vertical shaft; and

f. means for withdrawing solid materials from the oxidation furnace.

7. The furnace of claim 6, wherein the means for feeding the moltenmaterial to the oxidation furnace comprise means for granulating themolten matte and feeding the granules to the oxidation furnace.

8. The furnace of claim 6, wherein the means for feeding the gas to theoxidation furnace comprise a preheater for the gas in order to controlthe temperature of the oxidation furnace.

9. The furnace of claim 6, wherein the oxidation furnace is a fluidizedbed furnace and wherein the means for controlling the temperature of theoxidation furnace comprise means for cooling the bed.

10. The furnace of claim 6, wherein the means for withdrawing solidmaterial from the oxidation furnace comprise a separator in the meansfor feeding the roasting gases from the oxidation furnace to the upperpart of the reaction shaft in order to remove the solids entrained inthe roasting gases prior to feeding the roasting gases to the upper partof the reaction shaft.

I]. The process of claim 1 comprising preheating the oxidizing gas fedto the oxidation zone.

12. The process of claim 1 wherein the oxidation ca pacity of theoxidation zone is controlled to correspond to the smelting capacity ofthe flash smelting furnace reaction shaft.

1. IN A PROCESS FOR FLASH SMELTING A RAW MATERIAL SELECTED FROM SULPHIDEORES AND CONCENTRATES, THE STEPS OF: A. FEEDING INTO AN OXIDATION ZONEMOLTEN MATTE FROM THE FLASH SMELTING FURNACE AND AT LEAST ONE OXIDIZINGGAS SELECTED FROM THE GROUP CONSISTING ESSENTIALLY OF AIR AND OXYGEN, B.WITHDRAWING ROASTING GASES AT ROASTING TEMPERATURE FROM THE OXIDATIONZONE, C. FEEDING TO AN UPPER PART OF A REACTION SHAFT OF A FLASHSMELTING FURNACE SAID ROASTING GASES TOGETHER WITH FUEL AND SAID RAWMATERIAL, AND D. CONTROLLING TEMPERATURE IN THE OXIDATION ZONE FORMAINTAINING THE OXYGEN CONTENT IN THE ROASTING GASES BETWEEN ABOUT 5PERCENT AND ABOUT 18 PERCENT BY VOLUME AND FOR MAINTAINING THE SO2CONTENT IN THE ROASTING GASES BETWEEN ABOUT 1 PERCENT AND ABOUT 10PERCENT BY VOLUME TO CONTROL THE RELATIONSHIP BETWEEN THE OXIDATIONCAPACITY OF THE OXIDATION ZON AND THE SMELTING CAPACITY OF THE FLASHSMELTING FURNACE REACTION SHAFT.
 2. The process of claim 1, comprisingfluidizing the molten matte in the oxidation zone to a fluidized bed andcontrolling the temperature of the oxidation zone by cooling said bed.3. The process of claim 1, comprising controlling the temperature of theoxidation zone by preheating the gas fed to the same.
 4. The process ofclaim 1, comprising controlling the temperature of the oxidation zone toa temperature of from 900*C to 2,000*C.
 5. The process of claim 1,further comprising separating solids entrained in the roasting gasesprior to feeding the roasting gases into the flash smelting reactionzone.
 6. In a flash smelting furnace of the type having a lower furnace,a vertical reaction shaft at one end of the lower furnace, means forfeeding fuel and a raw material of sulphide ores or concentrates to theupper part of the vertical reaction shaft, and means for withdrawingmolten matte from the lower furnace: a. an oxidation furnace; b. meansfor feeding the molten matte from the lower furnace to the oxidationfurnace; c. means for feeding at least one gas selected from the groupconsisting essentially of air and oxygen to the oxidation furnace; d.means for controlling the temperature of the oxidation furnace; e. meansfor feeding hot roasting gases from the oxidation furnace to the upperpart of the vertical shaft; and f. means for withdrawing solid materialsfrom the oxidation furnace.
 7. The furnace of claim 6, wherein the meansfor feeding the molten material to the oxidation furnace comprise meansfor granulating the molten matte and feeding the granules to theoxidation furnace.
 8. The furnace of claim 6, wherein the means forfeeding the gas to the oxidation furnace comprise a preheater for thegas in order to control the temperature of the oxidation furnace.
 9. Thefurnace of claim 6, wherein the oxidation furnace is a fluidized bedfurnace and wherein the means for controlling the temperature of theoxidation furnace comprise means for cooling the bed.
 10. The furnace ofclaim 6, wherein the means for withdrawing solid material from theoxidation furnace comprise a separator in the means for feeding theroasting gases from the oxidation furnace to the upper part of thereaction shaft in order to remove the solids entrained in the roastinggases prior to feeding the roasting gases to the upper part of thereaction shaft.
 11. The process of claim 1 comprising preheating theoxidizing gas fed to the oxidation zone.
 12. The process of claim 1wherein the oxidation capacity of the oxidation zone is controlled tocorrespond to the smelting capacity of the flash smelting furnacereaction shaft.